A. Field of the Invention
The present invention is directed to head gimbal assemblies utilized in hard disk drive assemblies. More specifically, the present invention pertains to a head gimbal assembly designed to reduce movement and rotation of components of the head gimbal assembly structure.
B. Description of the Related Art
Presently, the hard disk drive industry is observing great success in the consumer electronics environment. One of the main reasons for this success is the ability to achieve ever increasing storage capacity reflecting consumer demand. So far, these advancements are being achieved with minimal cost compared to other competitive technologies.
However, continuing these advances require overcoming arising design and manufacturing difficulties. These difficulties can be found both in the drive level and the component level.
Hard disk drives (HDD) are normally utilized as the major storage units in a computer. Generally, HDDs operate by retrieving and storing digitized information stored on a rotating disk. This retrieving and storing (i.e., “reading” and “writing”) is done by a magnetic “head” embedded on a ceramic “slider” which is mounted on a “suspension”. The assembled structure of slider and suspension is usually called the head gimbal assembly (HGA).
A typical slider body is shown in FIG. 1. As shown in FIG. 1, an air bearing surface (ABS) design 102 known for a common slider 104 may be formed with a pair of parallel rails 106 and 108 that extend along the outer edges of the slider surface facing the disk. The two rails 106 and 108 typically run along at least a portion of the slider body length from the trailing edge 110 to the leading edge 112. The leading edge 112 is defined as the edge of the slider that the rotating disk passes before running the length of the slider 104 towards a trailing edge 110. The transducer or magnetic element is typically mounted at some location along the trailing edge 110 of the slider as shown in FIG. 1.
The operation of a typical slider is shown in FIG. 2. A suspension 204 supports the head gimbal assembly (HGA) 202 over the moving disk 206 (having edge 208) and moving in the direction indicated by arrow 210. Suspension 204 typically consists of multiple components, including a loadbeam, gimbal, electrical traces, a hinge and a baseplate. In operation of the disk drive, as shown in FIG. 2, an actuator 212 moves the HGA over various diameters of the disk 206 (e.g., inner diameter (ID), middle diameter (MD) and outer diameter (OD)) over arc 214.
In order to achieve maximum hard disk drive performance, the head must fly as close to the surface of the disk as possible while still maintaining a consistent, required spacing. This spacing is also known as the “flying height” or “magnetic spacing” of the disk. When a disk is rotated, it carries with it a small amount of flowing air (substantially parallel to the tangential velocity of the disk) on its surface that acts to support a magnetic head flying above, thereby creating the “flying height” of the head above the disk. Typically, the slider supporting the head is aerodynamically shaped to use the flow of this small amount of air to maintain a uniform distance from the surface of the rotating disk (e.g., 10 nm), thereby preventing the head from contacting the disk. The surface of the magnetic head closest to the disk (and being supported by the flowing air) is referred to as the “air bearing surface”. In order to make the slider fly stably and reliably in such a small gap, various design and geometric criteria including vertical stiffness (Kz), gimbal pitch and roll stiffness (Kp,Kr), gimbal static attitude—including pitch and roll attitude (PSA/RSA), and operational shock performance (G/gram) must be optimally designed and maintained to ensure performance.
In FIG. 1, the rails 106 and 108 form the air bearing surface on which the slider flies, and provide the necessary lift upon contact with the air flow created by the spinning disk. As the disk rotates, the generated wind or air flow runs along underneath, and in between, the slider rails 106 and 108. As the air flow passes beneath the rails 106 and 108, the air pressure between the rails and the disk increases thereby providing positive pressurization and lift. In general, as the air bearing surface area increases, the amount of lift created is also increased. Therefore, as a design criteria, there is a need for a method that allows for design of a flying height constituting the minimal amount of spacing between the head and the disk required for successful operation of the hard disk drive.
In addition, the flying height and the surface roughness of the disk drive components must be designed to preserve the mechanical operating parameters of the head, such as crown, camber and twist. The “crown” represents a deformation in shape along forward and aft directions of the slider (as shown by the Y-Y plane), and the “camber” represents a deformation in shape along lateral directions of the magnetic head slider (as shown by X-X plane). Crown and camber are shown in FIG. 3.
Another requirement is the suspension assembly have little or no “dynamic effect” on the performance of the slider air bearings. A dynamic effect is the result of head-disk contact. This may result from contact, or operation in higher altitudes where the air is thinner (thereby lowering the flying height). As a result, the suspension and the slider are both set into motion, causing the dynamic effect.
Besides those operational requirements, HGAs need to meet some non-operational requirements, such as non-operational shock robustness. During a shock event, the solder joining the individual component parts of the HGA experience stress. When the stress level experienced by the solder joints is higher than the strength of the material, cracks may begin to form, thereby jeopardizing the operational performance of the disk drive. In addition, with the continuous application of the stress on the solder joints, the components of the HGA may bend, further jeopardizing operational performance.
Furthermore, the forces experienced by the HGA during the shock event may disrupt the electrical trace connections in the HGA. Typically, during these shock events, the force on the HGA may cause the tongue and the slider to rotate, thereby pulling trace connections away from soldered joints and increasing stress. Such stress and deformation typically leads to operational failure.
Therefore, in order to maintain the structural and electrical connectivity integrity of the solder joints and maintain the operational design shape of the ramp limiter, a more optimum design geometry for the flexure is desired.